Abstract:
U.S. Population Grids (Summary File 3), 2000: Metropolitan Statistical Areas contain grids of demographic and socioeconomic data from the year 2000 U.S. census in ASCII and geotiff formats for 50 metropolitan statistical areas with at least one million in population. The grids have a resolution of 7.5 arc-seconds (0.002075 decimal degrees), or approximately 250 square meters. The gridded variables ... are based on census block geography from Census 2000 TIGER/Line Files and census variables (population, households, and housing variables). This dataset is produced by the Columbia University Center for International Earth Science Information Network (CIESIN).

The data in American Standard Code for Information Interchange (ASCII) and Geographic Tagged Image File Format (GeoTIFF) files and maps in Portable Document (PDF) and Portable Network Graphics (PNG) formats are available from the NASA Socioeconomic Data and Applications Center (SEDAC).

Purpose:
To provide gridded demographic data, including characteristics of income, education, and housing, for metropolitan statistical areas at a finer resolution than is available in the 30 arc-second grids used for the United States as a whole.

Quality
1. The 2000 SF3 files for each state are loaded into Microsoft Access and queries are used to extract the records pertaining to census blocks and the fields being used for gridding.

... 2. The SF3 fields are combined as specified in the variable documentation to create the variables being gridded.

3. The census blocks in a given metropolitan statistical area of more than one million in population are selected.

4. The SF3 block group data are proportionately allocated to the census block using an appropriate variable from the Summary File 1 data. For instance, the residents in the block group with a high school degree are allocated to the block using the population age 25 and older from SF1.

5. The SF3 counts assigned to each census block are joined to the tiger coverages. The density of each variable is calculated for each census block.

6. A 30 arc-second fishnet is created and unioned with the census block coverage.

7. The area in square kilometers is calculated for each area of intersection. The total count for each variable is calculated by multiplying the area in square kilometers in each area of intersection by the density of that variable in the underlying census block.

8. The total count for each grid cell is calculated by aggregating the variable counts for each area of intersection that falls within that grid cell.

9. The fishnet grid for each variable is converted to raster format.

Access Constraints
None

Use Constraints
Users are free to use, copy, distribute, transmit, and adapt the work for commercial and non-commercial purposes, without restriction, as long as clear attribution of the source is provided.